title: Structural studies of polymer hydrogel and silicone hydrogel contact lenses by means of positron lifetime spectroscopy methods.
abstract: PURPOSE OF JOB: Currently, there isa need to increase comfort and visual acuity man. Simultaneously improving biocompatibility and minimizing the impact of the material on the physiology of the cornea is the primary driving force behind the evolution of materials used in the manufacture of contact lenses. Despite progressive development of modern materials science, there is still the problem of reducing the level of oxygen available to the cornea resulting in pathological changes in the cornea. Therefore, structural studies increases interesting in relating to the amorphous contact lenses polymeric materials.
  
  
  METHODS
  The aim of this work is structural investigation of polymer hydrogel and silicone hydrogel contact lenses made in the technology of PC (Phosphoryl Choline). The study method was used positron lifetime spectroscopy PALS.
  
  
  RESULTS
  As a result of the measurements obtained curve describing the dependence of the number of counts of acts of annihilation as a function of time.
  
  
  CONCLUSIONS
  The study of PALS showed the existence of three components. Component tau1 is responsible for the annihilation of free positrons and the annihilation of electrons vacancy-type point defects. Component tau2 is associated with defects in the volume of grain boundaries formed, dislocations or clusters of vacancies. The results of calculations of mean values positron lifetime samples, showed longtime component tau3 in the spectrum of positron lifetime. Component tau3 is assigned to pick-off annihilation of ortho-positronium o-Ps trapping by free volume and providing information on the geometric parameters of the volume.
authors.affiliation: Institute of Physics, Jan Dlugosz University, al. Armii Krajowej 13/15, 42-200 Czestochowa, Poland.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Kotynia
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Kocela
authors.forename: Jacek
authors.initials: J
authors.lastname: Filipecki
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Filipecka
authors.forename: Piotr
authors.initials: P
authors.lastname: Korzekwa
authors.forename: Edmund
authors.initials: E
authors.lastname: Golis
mesh_terms: D001672:Biocompatible Materials; D003261:Contact Lenses; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000032:analysis / Q000737:chemistry; D008422:Materials Testing; D011108:Polymers / Q000737:chemistry; D012828:Silicones / Q000737:chemistry; D013057:Spectrum Analysis; D016875:tau Proteins / Q000032:analysis / Q000737:chemistry
chemical_list: D001672:Biocompatible Materials; D011108:Polymers; D012828:Silicones; D016875:tau Proteins; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate